The invention relates to a closure element for a pot equipped with a neck in order to confine a product, particularly a cosmetic product, in this pot in a tamperproof manner, the closure element being produced by dual-injection of plastic and including a fastening ring fixed onto the neck of the pot in a practically non-removable manner, this fastening ring being produced from a first plastic, and a disc, forming a lid, produced from a second plastic and connected to the fastening ring, this disc being equipped with a pull means, it being necessary to separate the disc from the fastening ring in order to open the pot.
There is known, for example from FR-A-2,617,756, a closure element of this type which is obtained by two successive injections, the conditions being chosen so that a connection becomes established by thermofusion in the zone of juxtaposition of the ring and of the disc, between the two materials of which these parts are composed.
Although this solution offers advantages, experience has shown that there was not really any control over the force of adhesion between ring and disc forming a lid, which leads to a significant spread in the forces required to tear the disc from the ring.